This invention relates to a bearing for rotary drums, such as for example tube mills, in bearing stations each with a plurality of shoe bearing elements distributed about the lower circumferential region and bracing the rotary casing from below.
In German patent document 43 16 579 A1, issued Nov. 11, 1994 to Klockner-Humboldt-Deutz AG, heavy ball mill casings are supported on a plurality of hydrostatically and/or hydrodynamically operated shoe bearing elements, for example on four such elements, arranged in distributed fashion about the lower rotary drum circumference. The rotary drum rests on cushions of pressurized oil, which is squeezed into the lubrication clearance between the four bearing shells and the braced rotary drum riding surface. All four shoe bearing elements are braced against the foundation via ball-and-socket joints and pairwise via a relatively costly articulated rocker lever construction.
If the radial distance of all shoe bearing elements from the rotary drum axis is not always set as equally great, it is not impossible that one bearing station with more than two neighboring shoe bearing elements becomes a statically indeterminate system. This is also the case for the bearing station disclosed in German patent document number 28 49 305, issued May 29, 1980 to Klockner-Humboldt-Deutz AG, in which a rotary drum is suspended in a belt-shaped steel band that completely encloses at least the lower half of the rotary drum and to the inside wall of which there are attached, for example, five sliding bearing elements spaced apart from one another but not all equally loaded. In this known bearing with the suspended rotary drum oscillating via the belt, the danger is furthermore not ruled out that, depending on the rotation speed of the supported rotary drum, the entire suspension bearing system and thus also the supported rotary drum can go into undesired operating conditions of resonance buildup and vibration.
It is an object of the invention to create a shoe bearing for heavy rotary drums, such as for example tube mills, which is designed in simple and lightweight fashion and in which it is guaranteed that all shoe bearing elements used at each bearing station are always uniformly loaded without resonance buildup at the bearing station.
While the weight forces of the supported rotary drum in the case of previously known shoe bearings are transmitted chiefly in the vertical direction into the foundation, in diametrically opposite fashion the weight forces of the supported rotary drum in the case of the shoe bearing according to the invention are redirected, by a carrying-cable support, largely into a horizontal direction and transferred into the foundation. At each bearing station, at least one of the two outlying shoe bearing elements is braced directly against the foundation while the other shoe bearing elements of the bearing station are fixed on a supporting cable. The supporting cable, stressed in tension, is capable of accepting and transmitting large tensile forces and thus large supporting forces. This supporting cable with the fixed shoe bearing elements has one end anchored on the foundation via a fixed bearing block and can be tensioned with a tensioning device or mechanism via the other end of the supporting cable. The bearing shells of the two outlying shoe bearing elements are supported on a spherical cap carried by the lower support part of the shoe bearing elements.
The supporting cable with the shoe bearing elements fixed thereto forms a sort of rope chain or link chain with full flexibility. The cable sections located between the neighboring shoe bearing elements can rotate or twist and also otherwise deform within certain limits. All four of the shoe bearing elements, or four hydrodynamic sliding bearings, distributed about the lower circumferential region of the rotary casing automatically adjust themselves so that the radial distance of all four bearing shells from the rotation axis of the supported rotary tube shell is always equal, even in case of flexures, changes of shape or changes of the inclination angle of the supported rotary casing. Thus all the shoe bearing elements are statically determinate and completely equally loaded without the necessity of costly control systems.
As a result of the carrying-cable support according to the invention, it is sufficient that the bearing shells of the outlying shoe bearing elements supporting the rotary casing each be supported by a spherical cap on the respective lower supporting part of the shoe bearing element. It may not be necessary to use a ball-and-socket joint in the shoe bearing elements lying in the central region, because the carrying cable permits articulation if the inclination angle of the supported rotary casing changes relative to the horizontal and/or if the rotary casing should flex or otherwise deform by certain amounts during its rotation.
Since at each bearing station at least one of the two outlying shoe bearing elements is supported directly on the foundation, resonance buildup and vibration is prevented by the shoe bearing of this invention. The carrying cable support, achieves all these advantages, and at the same time it is still designed in comparatively lightweight fashion and can be fabricated economically. Additionally, the shoe bearing of this invention, with carrying cable support, permits easy and rapid height adjustment of the supported rotary drum, and the rotary drum bearing housing sealing can be designed in simple fashion.
According to a further feature of the invention, the supporting parts of the bearing shells of the shoe bearing elements, may be fixed on the supporting cable by a clamp-block connection. The shoe bearing elements at each bearing station, arranged in distributed fashion about the lower rotary casing circumferential region can also, however, be flexibly connected to one another by a flexible support in the form of a link chain.
According to a further feature of the invention, the device for tensioning or retensioning of the supporting cable may include an arm holding the free end of the supporting cable, the arm being pivotally connected to the foundation via a pivot whose axis is substantially parallel to the axis of the supported cylindrical casing.